运行 case 语句时转换失败错误

Question

当我运行以下 case 语句时，出现错误“将 varchar 值 'NO' 转换为数据类型 int 时转换失败”。有人可以告诉我我在这里做错了什么吗？谢谢

,CASE
         WHEN DATEDIFF(DAY, convert(VARCHAR, Deliveries.DUE_DATE, 10), convert(VARCHAR, DELIVERIES.OB_DELIVERY_DATE, 10)) > 0
                THEN DATEDIFF(DAY, convert(VARCHAR, Deliveries.DUE_DATE, 10), convert(VARCHAR, DELIVERIES.OB_DELIVERY_DATE, 10))
         WHEN DATEDIFF(DAY, convert(VARCHAR, Deliveries.DUE_DATE, 10), convert(VARCHAR, DELIVERIES.OB_DELIVERY_DATE, 10)) < 0
                THEN DATEDIFF(DAY, convert(VARCHAR, Deliveries.DUE_DATE, 10), convert(VARCHAR, DELIVERIES.OB_DELIVERY_DATE, 10))

          ELSE 'NO'

       END AS DAYS_BEFORE_DUE_DATE

Answer 1

在case语句中只能返回一种数据类型。但是您可以使用 NULL 而不是 NO.

Answer 2

在这种情况下，您可以像这样转换 DATEDIFF 函数的结果：

select CASE WHEN DATEDIFF(DAY, convert(VARCHAR, Deliveries.DUE_DATE, 10), convert(VARCHAR, DELIVERIES.OB_DELIVERY_DATE, 10)) > 0
            THEN convert(varchar, DATEDIFF(DAY, convert(VARCHAR, Deliveries.DUE_DATE, 10), convert(VARCHAR, DELIVERIES.OB_DELIVERY_DATE, 10)))
            WHEN DATEDIFF(DAY, convert(VARCHAR, Deliveries.DUE_DATE, 10), convert(VARCHAR, DELIVERIES.OB_DELIVERY_DATE, 10)) < 0
            THEN convert(varchar, DATEDIFF(DAY, convert(VARCHAR, Deliveries.DUE_DATE, 10), convert(VARCHAR, DELIVERIES.OB_DELIVERY_DATE, 10)))
            ELSE 'NO'
       END AS DAYS_BEFORE_DUE_DATE
from Deliveries

Here is a demo

Answer 3

正如 Larnu 的评论所表明的那样，问题是 case 表达式 中的混合数据类型之一。（TSQL 没有 case 语句。）

猜测：Due_Date 和 OB_Delivery_Date 可能是 Date 列。如果是这样，您可以简单地使用 DateDiff 来计算天数的差异：

DateDiff( day, Deliveries.Due_Date, Deliveries.OB_Delivery_Date )

由于两个 then 子句 return 具有相同的值，因此可以将它们合并：

case when DateDiff( day, Deliveries.Due_Date, Deliveries.OB_Delivery_Date ) != 0
  then Cast( DateDiff( day, Deliveries.Due_Date, Deliveries.OB_Delivery_Date ) as VarChar(3) )
  else 'NO' end as Days_Before_Due_Date

注意Cast用于将数值转换为字符串

如果你想处理 early/on time/late 你可以使用 Sign:

case Sign( DateDiff( day, Deliveries.Due_Date, Deliveries.OB_Delivery_Date ) )
  when 1 then 'Late'
  when 0 then 'On Time'
  when -1 then 'Early'
  end as ScheduleStatus

运行 case 语句时转换失败错误

Conversion failed error when running case statement

sql

tsql

varchar